Advances in the field-theoretic understanding of pion production in nucleon-nucleon collisions

Abstract

We study the production amplitude for the reaction $NN\to NN\pi$ up to next-to-leading order in chiral perturbation theory. We show that the irreducible chiral loops at this order exactly cancel those terms that arise from the off-shell parts of the $\pi N$ rescattering vertex. This cancellation is required for formal consistency of the whole scheme. The net effect of the inclusion of all next-to-leading order loops is to enhance the leading rescattering amplitude by a factor of 4/3 compared to phenomenological studies, bringing its contribution to the cross section for $pp\to d{\pi }^{+}$ close to the experimental value.

Comments: To appear in the proceedings of the international conference MESON 2006, Cracow, Poland, 9 - 13 June 2006; 4 pages, 2 figures, uses ws-ijmpa.cls